Description

The T7121 HDLC Interface for ISDN (HIFI-64) connects serial communications links carrying HDLC bitsynchronous data frames to 8-bit microcomputer systems. There is an optional transparent mode of operation in which no HDLC processing is performed on user data. The device communicates with the system microprocessor as a memory-mapped peripheral and is controlled by reading and writing 19 internal registers. The chip can be instructed to interrupt the microprocessor when it detects certain events requiring microprocessor attention.

Features

■ Low-cost device for B-channel (64 kbits/s) or D-channel (16 kbits/s) data transport.

■ Optional transparent mode—no HDLC framing is performed.

■ Frame sync (FS) allows a slot-select feature to access an individual time slot in any TDM data stream (e.g., Lucent Technologies Microelectronics Group Concentration Highway Interface [CHI] or subset).

■ Bit-masking option allows effective data rates of 8, 16, 24, 32, 40, 48, and 56 kbits/s.

■ Maximum data rate up to 4.096 MHz.

■ Serial data-transfer pins for direct connection to the Lucent ISDN line transceiver T7250C.

■ Supports IOM2, K2, GCI, and SLD interface.

■ Parallel microprocessor interface with either multiplexed or demultiplexed address and data lines for easy interface with any microprocessor.

■ Single interrupt output signal with seven maskable interrupt conditions.

■ Programmable interrupt modes.

■ Memory-mapped read and write registers.

■ TTL/CMOS compatible input/output.

■ 3-state output pins to assist system diagnostics.

■ Low-power 1.25 µm CMOS:

— 30 mW typical operation at 12 MHz.

— 5 mW standby mode (typical).

■ HDLC transceiver:

— Stand-alone HDLC framing operation.

— 64-byte FIFO in both transmit and receive directions.

— Supports block-move instruction.

— Multiple frames allowed in FIFO.

— Programmable FIFO full- and empty-level interrupt.